Earth-boring tools are commonly used for forming (e.g., drilling and reaming) boreholes or wells (hereinafter “wellbores”) in earth formations. Earth-boring tools include, for example, rotary drill bits, core bits, eccentric bits, bicenter bits, reamers, underreamers, and mills.
Different types of earth-boring rotary drill bits are known in the art including, for example, fixed-cutter bits (which are often referred to in the art as “drag” bits), rolling-cutter bits (which are often referred to in the art as “rock” bits), diamond-impregnated bits, and hybrid bits (which may include, for example, both fixed cutters and rolling cutters). The drill bit is rotated and advanced into the subterranean formation. As the drill bit rotates, the cutters or abrasive structures thereof cut, crush, shear, and/or abrade away the formation material to form the wellbore.
The drill bit is coupled, either directly or indirectly, to an end of what is referred to in the art as a “drill string,” which comprises a series of elongated tubular segments connected end-to-end that extends into the wellbore from the surface of the formation. Often various tools and components, including the drill bit, may be coupled together at the distal end of the drill string at the bottom of the wellbore being drilled. This assembly of tools and components is referred to in the art as a “bottom hole assembly” (BHA).
The drill bit may be rotated within the wellbore by rotating the drill string from the surface of the formation, or the drill bit may be rotated by coupling the drill bit to a downhole motor, which is also coupled to the drill string and disposed proximate the bottom of the wellbore. The downhole motor may comprise, for example, a hydraulic Moineau-type motor having a shaft, to which the drill bit is attached, that may be caused to rotate by pumping fluid (e.g., drilling mud or fluid) from the surface of the formation down through the center of the drill string, through the hydraulic motor, out from nozzles in the drill bit, and back up to the surface of the formation through the annular space between the outer surface of the drill string and the exposed surface of the formation within the wellbore.
Fixed-cutter drill bits typically include a plurality of cutting elements that are attached to a face of bit body. The bit body may include a plurality of wings or blades, which define fluid courses between the blades. The cutting elements may be secured to the bit body within pockets formed in outer surfaces of the blades. The cutting elements are attached to the bit body in a fixed manner, such that the cutting elements do not move relative to the bit body during drilling. The bit body may be formed from steel or a particle-matrix composite material (e.g., cobalt-cemented tungsten carbide). In embodiments in which the bit body comprises a particle-matrix composite material, the bit body may be attached to a metal alloy (e.g., steel) shank having a threaded end that may be used to attach the bit body and the shank to a drill string. As the fixed-cutter drill bit is rotated within a wellbore, the cutting elements scrape across the surface of the formation and shear away the underlying formation.